1. Technical Field
This invention relates generally to watercraft, and more particularly to a motorboat or sailboat form of watercraft having at least one displacement body that produces a bow wave.
2. Description of Related Art
Motor and sail powered displacement boats generate a bow wave, followed by a trough and stem wave, due to hull form and friction. For a displacement boat, the bow wave increases in amplitude with boat speed until propulsion power is insufficient to climb the wave (i.e., the hull speed limit). The bow wave, when generated, initially moves forward at the hull speed, but eventually loses speed and moves at an angle away from the hull. When the bow wave does so, it has sufficient energy to threaten other nearby boats and cause damage to foundations at the water/land interface in narrow waterways. In addition, engines mounted on the stem of the boat generate strong propeller wave action and noise pollution, which are especially objectionable to residences and/or commercial buildings located near the water/land interface. These problems are accentuated when boats operating at low speeds are required to make sharp-angle turns in narrow waterways, such as in the canals of Venice, Italy. Because a rudder is less effective under such conditions, an articulating outboard motor (or propeller), which accentuates the generation of waves and noise pollution, may be required.
The problems associated with the operation of smaller displacement boats powered by stern-mounted internal combustion engines include:
1. Conventional power boats are designed as either: (a) displacement boats, efficient at low speeds but with sufficient power and planing surface to transcend the hull speed limits; or (b) planing boats, inefficient at low speed but with sufficient power and planing surface to transcend the hull speed limits; PA1 2. As mentioned above, bow waves generated by a boat move forward initially at the boat speed, but thereafter at decreasing speed due to friction, leading to potentially destructive bow waves moving laterally away from the boat; PA1 3. A significant portion of propulsion energy is lost when converted into wave energy, leading to inefficiency; PA1 4. Bow and stern waves plus stern-mounted propeller wave action generated by boats operating at high speed can cause serious damage to other boats and to foundations at the water/and interface in narrow waterways and small lakes; and PA1 5. Wave, noise, and air pollution generated by conventional displacement boats powered by internal combustion engines are accentuated with an articulating outboard motor or propeller.
Conventional twin-hull catamarans, motor or sail powered, are also displacement boats that generate bow waves followed by troughs and stern waves due to hull form and friction. They offer certain advantages over conventional mono-hull watercraft in their high lateral stability and reduced form and friction drag. Although increasingly popular, both sail and motor powered conventional catamarans suffer important disadvantages. Among other things, motor powered catamarans generate large bow waves at high speeds which threaten other nearby boats and foundations at the water/land interface. In addition, they generate substantial external noise pollution. Furthermore, neither motor or sail powered catamarans recover energy from the bow waves and thus they remain displacement boats and this limits propulsion efficiency at higher speeds.